Bird species richness within beaver ponds in south-central New York

We surveyed 70 wetlands during winter and spring 1992 to determine the influence of beaver activity on species richness of birds. Wetlands were divided into 3 activity types (active, inactive, potential), and 3 size categories of small (<2.5 ha), medium (≥2.5 <5.0 ha), and large (≥5.0 ha). We recorded 32 species of birds during winter, 20–25 within each activity/size category. There were no differences (P>0.050) among size classes in the average number of species/wetland, but the average was greater (P<0.050) in potential (4.7) versus active sites (3.1). We detected 106 species in spring, 92% of which were in active sites. Active sites also contained the highest (P<0.050) average number of species/wetland (29) compared to inactive sites (24) and potential sites (22). Active sites contained more open water, dead standing trees, surface water, and flooded emergents than inactive or potential sites. Wetland area (log transformed) was most correlated (r=0.43–0.56) with richness of birds in all activity categories. Overall, beaver occupancy of wetlands may have affected bird richness most by creating intermediate ratios of cover:water.